This invention relates to military defense of a tank or similar structure subject to enemy missile attack. The invention contemplates an electronic mechanim for generating an electromagnetic field in the vicinity of the tank; the electric field is intended to have a power level that is sufficient to bring the tank's emitted radiation into approximate equivalency to the power intensity of radiation emitted by the background scene (trees, buildings, etc.). The invention seeks to substantially eliminate contrast between tank radiation and background radiation, thereby defeating the target-detecting abilities of the radiation-detection sensor in the enemy missile.
The invention was prompted by recent development of missile-guidance passive sensors operating in the millimeter wave portion of the electromagnetic spectrum. The term "passive" is here used to mean a sensor that responds to naturally occurring thermal emissions from the target (tank), as opposed to reflected signals resulting from target-seeking signals generated by mechanism contained within the missile. The absence of a specially-generated detector signal is advantageous for such reasons as reduced risk of sensor (missile) detection, reduced weight and power consumption by the missile guidance system, and reduced possibility of active jamming by the tank countermeasures system.
Passive missile guidance systems using millimeter waves at selected frequencies (e.g. 35 GHz or 94 GHz or 140 GHz) are believed to have the following general advantages: relatively low propagation losses (from the target to the sensor); satisfactory target detection with a reasonably small antenna aperture; and operability in particulate-laden atmospheres such as fog, rain or smoke. The major limitation of such systems appears to be a relatively low operating range of about 2 kilometers (in smoky atmospheres).
It is presently believed that an enemy would utilize passive mm wave sensors as missile guidance devices when faced with tank attack in bad weather or under smoky, dusty battlefield conditions. The present invention is viewed as an add-on countermeasures device for the tank to defeat the mm wave sensor in the enemy missile.